Telephone system



May 21 1935. TO EY Er AL 2,002,212

VTELEPHONE SYSTEM Filed March 24, 1933 2 Sheets-Sheet l ,NVENTORS .J TOO/14E) WE HOGAN A TTORNEV May 21, 1935,

J. F. TOOMEY ET AL TELEPHONE SYSTEM Filed March 24, 1933 2 Sheets-Sheet 2 J. F. TOOMEY n! E. HOGAN INVENTORS ATTORNEY UNITED STATES PATENT OFFICE TELEPHONE SYSTEM John F. loomey, New York, N. Y., and Walter E.

Hogan,

South Boston, Mass, assignors to Bell Telephone Laboratories, Incorporated, New

York, N. Y., a corporation of New York Application March 24, 1933, Serial No. 662,428

22 Claims.

This invention relates to transmission systems and more particularly to the transmission efficiency means for controlling of such systems.

In telephone toll lines equipped with terminal 5 repeaters, for example, the transmission may be controlled by switching artificial lines into or out of the circuits in order to'lower or to raise their transmission levels. are known as pads.

These artificial lines This invention relates to means for controlling said pads by means of simplex circuits over the conductors of the operators cord circuit and the toll lines. An object of the invention is to control the transmission pad over a simplex circuit without shunting the ringing and signaling currents.

Another object is to control a termination for a transmission line by means of the pad control equipment and to connect said termination acrosssaid line when a cord is opened by the operation of a ringing or a splitting key.

Still another object is to connect a pad in each of two lines when a ringing, splitting or talking key of a cord circuit connecting them is operated.

A further object isto disconnect the simplex circuit from the cord circuit when the simplex is not required. A still further object is lowing description, together with the accompanying figures of the drawings in. which forms of the invention are illustrated.

Fig. l of the drawings shows toll switchboard circuits at a toll center and comprising toll line A arranged for pad control, a tributary toll line B, .a toll switching trunk C, a toll tandem trunk D, a toll cord circuit E for interconnecting said lines and trunks, and an operators telephone circuit F, the circuits being arranged according to the invention to provide pad control on the toll line when required on the various connections.

Fig. 2 of the drawings show combined local and toll switchboard circuits comprising a toll line G arranged for pad control, a tributary toll line H, a trunk or subscribers line I, a toll cord circuit J, and operators telephone circuit K, arranged according to a modified form of the invention.

Circuit description In Fig. 1 the toll line A connecting a distant toll center isprovided with a two-way terminal repeater I for amplifying the talking and signaling currents passing over the line in either directionb-Transmission pad IOI comprising an to place the pad control equipment at a point remote fromthe switchboard. I

An additional object is tandem trunk circuits.

to control the pad over Other objects will be evident from the specification and claims as set forth below.

A feature of the present invention whereby the above stated objects are attained resides in connecting an arm of the simplex bridge to the tip conductor at each end of the cord circuit and in reversing the tip and ring cord circuit.

Another feature resides through the simplex only toll cord are connected to actor.

conductors within the when both ends of the lines of certain char- An additional feature resides in shunting the pad control relays by a low resistance simplex bridge on certain connections.

A further feature resides in connecting the termination for the transmission'line across said line by means of equipment associated with the line whenever a splitting or ringing key is operated.

Still another feature resides in means in the toll cord for disconnecting the simplex circuit on connections where it is not required.

The invention will be un derstood from the fol- H-type network shown within the dotted line box is normally inserted in the line. This pad prevents overloading of the repeater I00 and also provides a means for regulating the transmission level of the telephone system in order that an approximately constant talking level will be provided for all types of connections. Connected to the tip and ring talking conductors respectively are relays I02 and I03 whose circuits pass through windings of retardation coil I04. The circuit through these relays and the retardation coil forms a simplex bridge across toll line A. Relays I02 and I03 will operate on battery connected to their respective talking conductors such as may be connected over a simplex circuit from the cord E. Slow release relay I will operate in response to the combined operation of relays I02 and I03 and connect a shunt circuit around pad W1 and open the bridge arm of the pad. Terminating network I00 is normally connected across the talking conductors when no cord circuit is connected to the line but is disconnected by the operation of sleeve relay IIO when a cord is connected. It may again be bridged across the line by the operation of relay I02 with relay I03 un operated. The toll line passes through the usual testboard jacks I01. The repeater, pad and associated pad control equipment may be in the same office with the switchboard or they may be in an office at a distance. Associated with the terminal is the usual signaling and supervisory equipment. The sleeve cut-off relay HE] is of comparatively low resistance (60 ohms, for example).

Tributary toll line B in the region of the toll center is not provided with transmission pads. The sleeve cut-01f relay N4 of this line is of high resistance (500 ohms, for example).

Toll switching trunk 0 arranged for straightforward operation terminates at the distant end in a plug at a local B or trunk switchboard at which appear multiples of subscribers lines. Trunk C has a high resistance sleeve relay I I8 (500 ohms, for example).

Tandem trunk D arranged for straightforward operation terminates at the distant end in a plug. I30 at a tandem switchboard at which may appear jacks of toll lines, toll switching trunks and of tandem completing trunks leading to other oflices. The jack sleeve relay I25 is of low resistance (57.5 ohms, for example) but normally has a high resistance I25 connected in series with it (442.5 ohms, for example) which is shunted responsive to the connection of the plug I39 at the tandem board with a toll line arranged for pad control.

Cord circuit E has its tip and ring conductors reversed at I El and is provided with arrangements for controlling the pad control equipment in the toll line on a connection thereto. The cord circuit and associated lines and trunks will be better understood by a description of their operation to be given later.

In Fig. 2, toll line G is similar to toll line A shown in Fig. 1, except that the sleeve relay ZII'I in line G is of high resistance (500 ohms, for example).

Tributary toll line H differs from tributary line B in having a low resistance simplex coil 252 bridged across the talking conductors.

A local subscribers line or trunk I is also terminated at this switchboard. It has a sleeve relay 254 of low resistance (34 ohms, for example).

Cord circuit J has its talking conductors reversed at 255i and, like circuit E has pad control equipment associated with it. These arrangements will be best understood from the follow- I ing description of their operation.

Operation When the operator at the distant end of toll line A (Fig. 1) rings over the line, the ringing current operates relay I85 associated with the incoming terminal. Relay I99 closes an operating circuit for relay II 2 which looks up under control of cut-ofi relay I I El and closes a circuit to light lamp III. At the end of the ringing interval relay Hi9 releases.

The answering operator noticing the lighted lamp inserts plug I32 of her answering cord into jack IE8. Low resistance cut-cit relay III], connected to the sleeve of jack I08 and marginal cord sleeve relay I33 operate over the sleeve circuits of cord and line from battery in the cord sleeve circuit. Relay Iii) opens the bridge circuits for relay IE9 and termination I05 and the locking circuit for relay IIZ releasing the latter which in turn extinguishes the lamp IIi. Marginal cord sleeve relay I33 which has operated over the low resistance sleeve circuit, closes its contacts preparing a path for the connecting of battery to the simplex on the cord talking conconnecting a small office ductors by marginal sleeve relay I 34 connected to the sleeve of calling plug I35.

The operator presses talk key H35 connecting her telephone set F to the cord and placing her in talking relation with the calling operator. The path prepared for the simplex circuit is opened at the auxiliary contacts of key 536.

Assuming first that a connection is desired to another toll line which we shall call Aa, identical to line A, the operator releases talk key I36 and inserts calling plug I35 into jack Ifi8a of line Aa (corresponding to jack MB of line A). Cut-01f relay Him in line Aa and marginal sleeve relay I34 in cord E operate on the current in the sleeve circuit. Sleeve relay I34 connects battery to the previously described path leading through contacts of the answering sleeve relay energizing the simplex circuit connected across the talking conductors of the cord. The simplex circuit, traced from battery passes through front contacts of calling sleeve relay I341, auxiliary contacts of talk key I36, front contacts of answering sleeve relay I 33 then dividing into two branches the first passing through the right-hand winding of impedance coil I31, back contacts of relay I 38 to the tip conductor of the answering cord and the second passing through the left-hand winding of the impedance coil, back contacts of relay are to the tip conductor of the calling cord. Since the tip and ring cord conductors are reversed at lSI within the cord the simplex is bridged across the talking conductors.

Current from the simplex battery, therefore, finds parallel paths over the two talking conductors to the talking conductors of both toll lines. Current flowing out over the tip conductor of line A finds a path to ground through the upper winding of retardation coil Hi l and relay I02. Current flowing over the ring conductor passes through the lower winding of coil Hit and relay I93 to ground. Relays i532 and E93 operate closing a circuit for the energization of slowrelease relay I 65. Relay I05 connects a shunt around the transmission pad IGI and opens the bridge arm of the pad. Pad IQIa of line Aa connected to the calling end of the cord is shunted in like manner.

The operator presses ringing key Mil associated with the calling cord thereby connecting ringing current to toll line Aa and opening both talking conductors of the cord between the connecting points for the simplex circuit. Thus, a conductor of the simplex circuit being opened, the simplex can not shunt the ringing current. Battery is thereby disconnected from the ring conductors of both the calling and called lines causing relays I 03 and Nita to release. Relays I95 and I 85a are thus deenergized and release thereby removing the shunt circuits around the pads IOI and IilIa, respectively, and closing the pad bridge arms. Since the tip connected pad control relay I02 remains operated from the simplex battery over the tip side of toll line A, the terminating network Illii is connected across the line, it being connected through front contacts of relay I02 and back contacts of relay I03. The pads in lines A and Ad in this case tend to stabilize the balance of their respective repeaters, and in the case of line A the terminating network IIlB is also connected across the line to further improve the repeater balance. In the case of line Ad, however, the ground connected to the tip side of the line by the ringing key M0 causes relay IBM to release, thereby opening the termination.

path of terminating network I 060. and preventing. it from shunting the ringing current. F Upon release of the ringing key, thepads; in both lines are again shunted and the termina-. tion on line A is removed due to the Ire-operation of relay Hi3. After ringing on this type of call, the operator ordinarily doesnothingmore until she receives a signal to. disconnect evidenced by the lighting of one of her cord supervisory lamps;

These lamps and their associated relays are not shown in the drawings since they are well known in the .art and the drawings would become unnecessarily complicated bytheir addition.

Supposing, however, that the operator wished to talk torboth parties duringthe connection. She would operate talk .key I36 to connect her telephone set. This would open the auxiliary contacts of. key I35 thusopening thetenergizing path for the simplex circuit; This would cause release of the pad control relays in the toll lines reconnecting the pads in both linesduring ,the time her talk key is operated. I .i H If the operator should wish-totalkto the distant .end oi? line A and excludeline Ad from the 25' conversation, she would operate talk key I36 and calling cord splitting key I42. The talk key opens the. simplex energizing circuit releasing the pad control relays in the lines and splitting key I42 closes at its auxiliary contacts an operating circuit for relay I38, which, in operating opens the simplex lead to the tip of the answering cord and connects battery to the simplex lead extending to the tip of the calling cord. Thisbattery on the tip conductor of line Aa operates relayv 162w connecting termination Iiiiia across the line. Thus the pads are reinserted in both lines and a terminationis connected across the held line. Similarly on talking only to line Aa splitting key I II isoperated instead of M2 and relays I39 and I02 function to connect a termination acrossline A. Release of the keys removes both pa'ds'and the On disconnection removal of one of the plugs reinserts the-pads in both lines by deenergizing the simplex. I

If tributary toll line B isto be connected to toll line A the operator upon receiving the call over line A releases her talk key I36 and connects plug- I35with jack H5. High resistance cut-off relay IM operates on the sleeve-current, but marginal calling cord sleeve relay I34 does not operate in this high resistance circuit. Battery is not connected to the simplex, therefore, and pad IOI in toll line A remains in the circuit. This is the de sired condition on such a connection. The pad control arrangements remain unoperated during the whole connection, except as follows: I

Should the operator wish to talk to a party at distant end of tributary line B while excluding line A from the conversational circuit, she would operate her talk key I36 and splitting key IM associated with her answering cord. Thus terminating network I 66 would be connected across line A as previously described. If instead of key MI, key I IZwere operated, energizing relay- I38,

the leadto the tip of the answering'cordwould be I opened and battery would be placed on the tip of the calling cord and line B, but since line B has no pad control or termination circuits nothing would occur thereon. No battery being connected to the tip of line A, the termination would remaindisconnected therefrom.

If the operator at the distant end of line A asks for a subscriber in the immediate area of the toll office, the answering toll operator 'connects'her calling 'cord to toll switching trunk vC leading to the local B board at; which the line multiple appears. Since the sleeve relay I I8 of this trunk is also of high resistance marginal calling cord sleeve relay. I34- does not operate in this high resistance circuit. Battery, therefore, is not connected to the simplex and pad IIII in toll line A remainsin the circuit. This is the desired condition on such aconnection. Sleeve relay I I8 con nects relay IZI across the trunk. Relays I2! and IE2 serveto relay supervisory signals back over the trunk to the toll cord.

The operator presses ringing key I40 causing ringing. current to operate A. C. relay I2!) in trunk C. -Relay IZII operates relay I23 which connects signaling current over the trunk. In this case the operator has. kept her talk key operated. When the B? operator is connected the toll operator gives her the number of the desired line and releases the talk key.

If the call incoming on line A must be routed through a tandem office, the operator connects plug I35 to jack I24 of tandem trunk D. Since the trunk sleeve relay I25 has a high resistance I26 in series with it, marginal cord sleeve relay I34 remains unoperated, while trunk sleeve relay I25 operates lighting-lamp I29 at the tandem board. The tandem operators telephone (not shown) is manually or automatically connected to the trunk and after the toll operator passes the call and releasesher talk key, the tandem operator connects plug I'3Il with a tandem completing trunk or with atoll line or trunk similar to A, B or C of Fig. 1. Assuming that the tandem trunk is connected to a toll line arranged for pad control whose sleeve has a low resistance to ground (60 ohms, for example) as at hi3, marginal relay I2? will operate in series with relay IZt andwill close a shunt across resistance I26 thus providing a low resistance sleeve circuit at the calling end of cord E and allowing marginal calling cord sleeve relay let to operate. Relay I34 energizes the pad control circuit thereby removing pad IEII from the calling line A and in addition energizing the simplex over tandem trunk D to remove the pad in the called toll line whose. sleeve is shown at Hi3; Relay I28 servesto extinguish lamp I29 and place it under control of the release of relay I25;

On a tandem call to a line or trunk not arranged for pad control and therefore having a high resistance (500 ohms, for example) sleeve circuit as shown at I44, marginal relay I21 does not operate with relay I28 and hence does not close a low resistance circuit for marginal relay 34. Under this condition the pad control circuits are not energized and pad IIlI remains in line A.

.When the tandem operator plugs into either type of .line or trunk the control is placed under the toll operator at cord circuit E so that operation of talking, ringing or splitting keys in cord E controls the pads and terminations (when present) of lines outgoing from the tandem switchboard in the same manner as if they were connected directly to cord plug I35.

. On disconnection the toll operator disconnects calling and answering cords. Tandem trunk relay I25 releases lighting lamp I29. The tandem operator then removes plug I39 from the jack and relay I28 releases extinguishing the lamp. i

In the case of a call incoming on tributary toll line B, the operator inserts answering cord plug. I 32 into jack H5. Since the line cut-ofi relay H4 is of high resistance marginal cord sleeve relay I33 does not operate and the simplex remains disconnected on all types of.con-.

nections. In case the call is extended by inserting calling cord plug I35. into the jack of toll line. A, however, and splitting key [42 is then operated, termination it will be connected across line A as will be understood fromthe' previous de! scription.

Referring to Fig. 2, the operator in answering a call incoming on toll line G inserts plug 232 into jack 2%. High resistance cut-oil? relay 2m and cord sleeve relay 233 operate on the sleeve current. It will be noted that in cord J the answering cord sleeve relay 233 is not marginal, hence will operate on high. resistance. sleeve circuits. Both relays function as previous-. ly described in connection with Fig. 1. The operator presses talk key 23.6 connecting her tele-.. phone set K which includes low resistance. simplex bridge 2%. Relay 26.0 operates under control of the talk key.

Assuming first that the call is intended for a second toll line Gg identical to G, the operator releasesher talk key 236 and inserts calling plug; 235 into jack 233 of line Gg. Cut-01f relay 2mg in line G and sleeve relay 2 34 in cord J operate but marginal sleeve relay 2,5! in cord. J. does not operate on the sleeve current. The. simplex is thereby energized by relays 233; and 23. 3 in the manner previously described for Fig. l and the pad control relays in lines G. and Gig operate to remove the pads from the circuit. Operation of the ringing key 2140-: removes the simplex battery from the ring side ofboth lines;

and thereby inserts the pads and terminating.

network as described for Fig. 1. Upon release of the ringing key, the pads and termination are again removed.

If the operator should press talk key 236.- under these conditions, low resistance retardation coil 2553., whose mid-pointis grounded will form a sim-.. plex bridge across the talking conductors, will efiectively shunt the high resistance sim-. plex bridgeson the toll lines, such as that on toll; line G comprising retardation coil 204' and pad: control relays 282 and 203, preventing suflicient' current from reaching the pad control relays to hold them operated. The relays in both toll. lines will release, therefore, reinserting the, pads. in the circuit.

If splitting key 242' is operated in this condi-- tion, relay 238 operates. connecting thesimplex. l'ead to the tip of the answering cor-d, through ups. per contacts of relay 280 which are closed as long as the talk keyis operated. The splitting. key: opens the talking conductors thereby removing the simplex battery from the ring conductor at each end and removing low resistance shunt 2-50 from the calling cord and called line Gg. Thus. battery over the tip of the called line inserts the termination 2536}; in the usual manner. The tip. relay in the called line is not shunted by bridge 256 over the simplex. leads from the tip of the answering cord due to resistance 2% in serieswith the lead to that cord. The tiprelay in the calling line, however, remains shunted by the bridge; hence the termination is not bridged across the calling line to. which the telephone set K is connected.

Similarly the operation of splitting key 2431 instead of 2 52, with the talk key operated,.c0n nects termination 72% across line G.

On a call to. tributary toll line H, calling: plug 235 is inserted in jack 215 of line H. High: re: sistance cut-.oif relay 2. and: cord sleeve relay 234i operate and marginal cord sleeve relay- 25]: remains unoperated, as before. Therefore, the

simplex connected across the cord and energized. Low resistance. simplex bridge 252 connected across the talking conductors of line H, however, eftectively shunts the simplex bridge on calling line G. comprising coil 204 and the pad control relays. The relays do not receive sufficient. current to. operated, therefore, and the pads consequently remain in the circuit on this connection.

Operation of ringing key 2410 removes simplex battery from the. ring side of each cord. terminal and also. removes the low resistance shunt 252 from the answering cord allowing simplex battery on the tip. of this cord to pass over line G operating relay 202 thus connecting termination 206-. Release of the ringing key removes the termination.

Operation of talk key 236 again connects the telephone circuit K and low resistance bridge 25BIto. the cord and operates relay 26%]. Opera! tion of splitting key 24.! operates relay 239 connecting the simplex battery to the calling cord through the now: closed lower contacts of relay 261]. Key 24 I1 also removes at its contacts simplex battery from the ring conductor of each end of the cord. Simplex battery on the tip of the answering cord will not be shunted by either low resistance bridge 25!! or 252' since the contacts of; key 24211 are open and resistance 25! is the lead to the tipof the calling cord. Hence relay 29.2 in line G operates connecting the termination.

If, instead, splitting key 242 is operated, the bridge, 2-50; shunts the pad control relays. leaving the termination disconnected.

Ona call from line G to a subscribers line (or trunk) I the operator inserts plug 235. into jack 253 of linezI. In this. case low resistance cut-off relayZaSA associated with line. I, cord sleeve relay 23.4: and marginal cord sleeve relay 25.! all operate. Relay 23.4 energizes the simplex circuit. Marginal relay" 25 however, closes a circuit. for the operation. of relays. 23.8 and 239 which disconnect the simplex from the. answering and call-- ing-ti'p. conductors; respectively. Relay 25! also connects the talkingv circuit through repeating- Qoil: 215.5; thereby opening the direct current. connectionof the,- talking conductors within the cord while preservin the talking connection. If ringng key: 2-40 is; operated, the simplex battery still remains; disconnected by relays 238- and 239. so nov termination placed across line G. Line G, in this case,, is; terminated in the cord circuit in repeating 001112-55.

It talk key; 2-36; is. operated, relay 26B. operates again connecting the simplex to the talking conductors, through its contacts and front contacts of: relays 2.38 and; 23B; Simplex battery on the tip of the nswering cordis shunted through bridge; 25,0 the telephone circuit. I-i splitting key' 2 H is operated, the shunt is removed thereby providin the simplex battery on the tip of calling line; G to connect the terminating network 206..

On- 21.0.3111 from tributary toll line H to subscribers, line; (01: trunk) I the pad control arrangements are. inop rative.

Although the. invention is shown and described as. embodied in certain specific arrangements, applicantsdo not wish to be limited by such disclosure, but desire to. cover broadly all arrangements. that come within the spirit and scope of the appended claims- What, is claimed is:-

1., In; a telephone system,v a telephone, line cir-.

between the tip talking conductorxat one end of the cord circuit andthetipta'lking conductor at the opposite end of said cord circuit. 7

,, 2. In a telephone" system, telephone line circuits, a cord circuit adapted to be. connected thereto,-the talking conductors of said cord being reversedbetween the ends thereof, means to connect a simplex circuit to the talking conductors of said line circuits comprising an impedance bridge between the tip talking conductorsatope posite ends of the cord circuitand asimplex lead connected to the mid-point of said bridge.

3. In a means to connect a simplex circuit over a telephone line, a line circuit comprising two conductors, a bridge across said line, a simplex lead connected to a middle point of said bridge, a cord circuit adapted to be connected; to said line circuit, the tip and ring conductors of said .cord circuit being reversed within the cord,-a second bridge, a simplex lead connectedtoa middle point of the secondbridge, said bridge being connected between the tip conductors at the opposite ends of the cord circuit.

4. In a telephone system, a transmission line, transmission regulating means associated therewith, a second line, a cord circuit for interconnecting said lines, the talking conductors of the cord circuit being reversed within said cord, a

simplex circuit including the talking conductors of said cord circuit and of said transmission line and comprising simplex bridges across said cord circuit and said transmission line, respectively, for controlling said transmission regulating means, the said bridge across said cord circuit being connected between the tip talking conductors at the two ends of the cord.

5. In a communication system, a transmission line, transmission regulating means associated therewith, a cord circuit connected to said line, means for controlling said regulating means comprising a simplex circuit on said line and cord talking conductors, said simplex circuit comprising a bridge connected from the first talking conductor at one end of the cord to the second talking conductor at the opposite end of the cord.

6. In a communication system, a transmission line, transmission regulating means associated therewith, a cord circuit connected to said line,

means for controlling said regulating means comprising a simplex circuit on said line and cord talking conductors, means to open both of said cord talking conductors, means to de-energize one side of said simplex responsive to the operation of said last means consisting of the connection of the simplex circuit to one of the cord talking conductors at one end of the cord and to the other at the opposite end of the cord.

'7. In a communication system, a transmission line, a cord circuit connected thereto, means to signal over said line comprising means in said cord circuit to open said talking conductors and to apply signaling currents across said conductors between said opening and said line, and means to connect a bridge across the talking conductors of said cord circuit without shunting said signaling currents comprising connections for said bridge from the first talking conductor at one end of 'said'cord to the second talking conductor at the opposite end of said cord.

'8. In a telephone system, a pair of telephone lines, transmission pads normally connected in each of said lines, a cord circuit for interconnecting said lines, and pad control means to effectively remove the pads from bothsaid lines responsive only to the connection of the cord circuit between said lines.

9. In a telephone system according to claim 8, talking and ringing keys within said cord circuit, said pad control means reinserting both of said pads on operation of any one of, said keys.

10. In a telephone system according to claim 8, a splitting key associated with each end of said cord circuit, saidpad control meansreinserting both said pads on operation of either of said keys.

11. In a telephone system according to claim 8, a splitting key associated with each end of said cord circuit, a terminating network associated with each said line, said pad control means connecting the terminating network associated with a first of said lines across said line responsive'to the operation of the splitting key associated with the end of the cord circuit connected to said line.

12. In a telephone system, telephone lines, transmission pads in said lines, a cord' circuit adapted to interconnect said lines, answering and calling sleeve relays in said cord circuit, and pad any one of said associated lines of either character, a simplex circuit comprising the talking conductors of said cord circuit and of said transmission line for controlling said transmission regulating means, and means responsive to the connection of said cordcircuit to said transmission line and a line of said first character only to control said transmission regulating means over said simplex circuit.

14. In a telephone system, a switchboard, a transmission line terminating thereat, transmission regulating meansassociated with said line, other lines of a first and also of a second character also terminating at the switchboard, a cord circuit for connecting said transmission line with any one of said associated lines of either character, a simplex circuit including the talking conductors of said cord circuit and of said transmission line for controlling said transmission regulating means, and means responsive to the connection of said cord circuit to said transmission line and a line of said first character only to energize said simplex circuit and control said transmission regulating means.

15. In a telephone system, a transmission line, transmission regulating means associated there with, a terminating network also associated therewith, a second line, a cord circuit for interconnecting said lines, a simplex circuit including the talking conductors of said cord circuit and of said transmission line and comprising simplex bridges across said cord circuit and said transmission line, respectively, for controlling said transmission regulating means, and means for controlling said terminating network comprising one of the talking conductors of said cord circuit and of said transmission line and one-half of the simplex bridges in said cord and line, respectively.

16. In a'telephone system, a transmission line, transmission regulating means associated there with, a terminating network also associated therewith, a second line, a cord circuit for interconnecting said lines, a simplex circuit including the talking conductors of said cord circuit and of said transmission line ion controlling said transmission regulating means, means responsive to the operation of a splitting key in any part of said cord circuit to open one of the talking conductors included in said simplex circuit to: remove control of said transmission regulating means and to control said terminating network over the remaining talking conductor.

17. In a telephone system, a trunk circuit, a cord circuit connected to one end of said trunk circuit, a telephone line connected to the other end of said'trunk circuit, transmission pads normally connected in said telephone line, and pad control means for controlling said pads from said cord circuit comprising a simplex circuit on the talking conductors of said cord, trunk and line circuits.

18. In a telephone system, a telephone line, transmission regulating means associated with said line, a cord circuit connected to said line, an operators telephone set adapted to be connected to said cord circuit, means comprising a simplex circuit on the talking conductors of said line and cord circuits to control said transmission regulating means, and a low resistance simplex bridge connected across said operators telephone set to effectively shunt the simplexcircuit on said line when said telephone set is connected to said cord circuit.

19. In a telephone system, a switchboard, a transmission line terminating thereat, transmission regulating means associated with said line, other lines of a first and also of a-second character also terminating at the switchboarda cord circuit for connecting said transmission line with any one of said associated lines of either charactor, a simplex circuit including the talking conductors of said cord circuit and of said transmission .line and comprising simplex bridges across said cord circuit and said transmission line, respectively, for controlling said transmission regulating means, means responsive to the connection of said cord circuit to said transmission line and a line of either character to energize said simplex circuit, and a low resistance simplex bridge across each line of said second character to shunt the simplex circuit from said cord circuit to said transmission line and prevent control of said transmission regulating means on connections to lines of said second character.

20. In a telephone system, a telephone line, a transmission pad in said line, a terminating network adapted to be connected across said line, a cord circuit connected to said line, pad control means comprisinga simplex circuit on the talking conductors of said line and cord circuit, and means for controlling said terminating network comprising one side of said simplex circuit.

21. In a telephone system, a telephone line circuit, transmission regulating means associated therewith, 'a-cord circuit, means associated with said cord for controlling said transmission regulating means, a trunk circuit adapted to interconnect said cord and line circuits, and means to render said cord circuit means eiiective responsive to the connection of said trunk between said cord and line circuits. 7

22. In a telephone system, a telephone line, a terminating network normally connected across said line, a-cord circuit, means to disconnect said terminating network responsive to the connection of said line andcord circuits, and means responsive to the operation of a ringing or splitting key in said cord circuit while connected to said line circuit to reconnect said network across said line.

JOHN F. TOOMEY. WALTER E. HOGAN. 

